Crosslinkable hydroxy terminated polydiene polymer coating compositions for use on substrates and a process for preparing them

ABSTRACT

A crosslinkable composition for coating primed and unprimed substrates comprising from 10 to 80 percent by weight of a hydroxy functional polydiene polymer having a functionality of at least 1.3, 8 to 60 percent by weight of an amino resin crosslinking agent, and 2 to 40 percent by weight of a reinforcing agent. The invention also encompasses a process to make such compositions by partially reacting the three components for 0.5 to 10 hours at 60 to 120° C., optionally in the presence of a small amount of catalyst, to give phase stable compositions and subsequently completely crosslinking the composition by baking the composition on a substrate. The invention also encompasses a process for painting a substrate which comprises priming the substrate with a primer selected from the group consisting of epoxy resin primers and polyester resin primers, applying to the primed substrate a crosslinkable basecoat composition comprising from 10 to 80 percent by weight of a hydroxy functional polydiene polymer having a functionality of at least 1.3, from 8 to 60 percent by weight of an amino resin crosslinking agent, and from 2 to 40 percent by weight of a reinforcing agent, and applying over the basecoat a clearcoat selected from the group consisting of dihydroxy polydiene-based clearcoats, polyester clearcoats, and acrylic clearcoats.

CROSSREFERENCE TO PRIOR APPLICATION

This application claims priority to provisional U.S. patent applicationsSer. No. 60/006,816, filed Nov. 16, 1995, and Ser. No. 60/028,378, filedOct. 15, 1996.

This is a division of application Ser. No. 08/748,291 now U.S. Pat. No.5,750,629, filed Nov. 13, 1996, the entire disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates to novel crosslinkable compositions comprised ofhydroxy terminated polydiene polymers, amino resins, and reinforcingagents. More specifically, the invention relates to the use ofparticular di- and poly-hydroxy terminated hydrogenated diene polymersin crosslinking with amino resins to produce products which are usefulin coating compositions which adhere well to substrates which have orhave not been coated with a suitable primer. These coating compositionsmay contain pigment and may be used to "paint" the substrate.

BACKGROUND OF THE INVENTION

Hydroxy functional polydiene polymers are well known. U.S. Pat. No.5,393,843 discloses that formulations containing these polymers, amelamine resin, and an acid catalyst can be cured by baking under normalbake conditions. This same patent also discloses that these polymers canbe mixed with isocyanates to yield compositions which cure at ambienttemperature. However, these compositions based on hydroxy functionalpolydiene polymers cured with a crosslinking agent are usually fairlysoft and, although they can be very useful in some applications, theyhave limited adhesion. Attempts to increase hardness and adhesion byincreasing crosslink density by simply mixing these components with areinforcing agent, such as a low molecular weight diol or triol, andhigher levels of crosslinking agent were unsuccessful because thereinforcers and crosslinkers are relatively polar and so areincompatible with the relatively nonpolar polydiene polymers.Incompatibility of the components leads to poor properties, such asgloss, in the cured composition or, even worse, the compositions mayphase separate upon storage prior to cure.

One potential use for these compositions is for direct application to anacceptable substrate such as a plastic automotive exterior part. Theyare also highly useful in coatings for use on substrates which havealready been coated with a primer coating. An example of this type ofapplication is in basecoat coatings (basecoats) in the automotiveindustry. The basecoat contains pigment and is the actual "paint" whichgoes onto the car. A clear coat is usually applied over the basecoat topreserve the color. One primary substrate to which the basecoats will beapplied is steel which has been primed with an epoxy resin based primerwhich was applied by the cathodic electrodeposition (CED) process.Another substrate which could be used is the epoxy primed steel whichhas also been coated with a primer/surfacer which is usually based on apolyester resin.

This invention presents novel compatible coating compositions preparedfrom these components which exhibit excellent adhesion to primed andunprimed substrates and provides a process for the preparation of thesenovel compositions. This invention thus provides a composition which maybe used to "paint" the entire exterior of an automobile.

SUMMARY OF THE INVENTION

The invention herein is a coating composition which is highly useful forcoating and painting a variety of unprimed substrates, such as plasticsurfaces including polyethylene, polypropylene, etc., and for paintingprimed substrates. Steel is the most common substrate which requirespriming and it is usually primed as described above. The coatingcomposition of this invention is a crosslinkable composition containinga hydroxy functional polydiene polymer, an amino resin crosslinkingagent, and a reinforcing agent which has at least two functional groupswhich will react with the amino resin crosslinker. The coatings of thisinvention will usually contain a pigment but it is not required. Thepreferred polymers for use herein are hydrogenated polydiene diols. Thepolymers must have a functionality of at least about 1.3 so that theywill actually crosslink. In a more preferred embodiment of theinvention, the diol will have a functionality of at least about 1.9. Inanother preferred embodiment of the invention, the diene polymer willcontain a substantial amount of a vinyl aromatic hydrocarbon, usuallystyrene, since coatings made from such polymers exhibit good adhesion tounprimed steel substrates as well.

In order to make the compositions of the present invention, the novelprocess of this invention must be followed. The diene polymer, the aminoresin, and the reinforcing agent are mutually incompatible and thereforecannot be used as merely a physical blend. Instead, they must bepartially reacted before they are cast as a film or otherwise usedinstead of being used as a blend which is crosslinked after application.The components should be "cooked" in a vessel for some combination oftime, temperature, and catalyst concentration sufficient to give acomposition which will not phase separate. Typical cooking conditionsare 0.5 to 10 hours, preferably 1 to 4 hours, at 60 to 120° C.,preferably 80 to 100° C., with about 0 to 0.4 parts by weight of acatalyst which is used to accelerate the reaction of the hydroxyls withthe amino resin. Complete crosslinking of the composition isaccomplished after the catalyst concentration is increased to therequisite level and the composition is applied to the substrate andbaked.

DETAILED DESCRIPTION OF THE INVENTION

Hydroxy functional polydiene polymers and other polymers containingethylenic unsaturation can be prepared by copolymerizing one or moreolefins, particularly diolefins, by themselves or with one or morealkenyl aromatic hydrocarbon monomers. The copolymers may, of course, berandom, tapered, block or a combination of these, as well as linear,radial or star.

The hydroxy functional polydiene polymers may be prepared using anionicinitiators or polymerization catalysts. Such polymers may be preparedusing bulk, solution or emulsion techniques. When polymerized to highmolecular weight, the polymer will, generally, be recovered as a solidsuch as a crumb, a powder, a pellet or the like. When polymerized to lowmolecular weight, it may be recovered as a liquid such as in the presentinvention.

In general, when solution anionic techniques are used, copolymers ofconjugated diolefins, optionally with vinyl aromatic hydrocarbons, areprepared by contacting the monomer or monomers to be polymerizedsimultaneously or sequentially with an anionic polymerization initiatorsuch as group IA metals, their alkyls, amides, silanolates,naphthalides, biphenyls or anthracenyl derivatives. It is preferred touse an organo alkali metal (such as sodium or potassium) compound in asuitable solvent at a temperature within the range from about -150° C.to about 300° C., preferably at a temperature within the range fromabout 0° C. to about 100° C. Particularly effective anionicpolymerization initiators are organo lithium compounds having thegeneral formula:

    RLi.sub.n

wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substitutedaromatic hydrocarbon radical having from 1 to about 20 carbon atoms andn is an integer of 1 to 4.

Conjugated diolefins which may be polymerized anionically include thoseconjugated diolefins containing from about 4 to about 24 carbon atomssuch as 1,3-butadiene, isoprene, piperylene, methylpentadiene,phenyl-butadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadieneand the like. Isoprene and butadiene are the preferred conjugated dienemonomers for use in the present invention because of their low cost andready availability. Alkenyl (vinyl) aromatic hydrocarbons which may becopolymerized include vinyl aryl compounds such as styrene, variousalkyl-substituted styrenes, alkoxy-substituted styrenes, vinylnaphthalene, alkyl-substituted vinyl naphthalenes and the like.

The hydroxy terminated polymers of this invention are generally diolswhen the polymer is linear. Radial and star polymers are alsocontemplated herein and in such case, the polymers would be polyolswherein a hydroxy group is located at the ends of most or all of thearms of such polymers.

The hydroxy functional polydiene polymers may have number averagemolecular weights of from about 500 to about 500,000. Lower molecularweights require excessive crosslinking whereas higher molecular weightscause very high viscosity, making processing very difficult. Morepreferably, the polymer is one having a number average molecular weightof from about 1,000 to about 50,000. Most preferably, the polymer is apredominately linear diol having a number average molecular weight offrom about 2,000 to about 20,000 because this offers the best balancebetween cost, ability to use the mildest curing conditions, andachieving good processing behavior.

Hydrogenated polybutadiene diols are preferred for use herein becausethey are easily prepared, they have low glass transition temperature,and they have excellent weatherability. The diols, dihydroxylatedpolybutadienes, are synthesized by anionic polymerization of conjugateddiene hydrocarbon monomers with lithium initiators. Polyols can besynthesized in the same manner. This process is well known as describedin U.S. Pat. Nos. 4,039,593 and Re. 27,145 which descriptions areincorporated herein by reference. Polymerization commences with amonolithium, dilithium, or polylithium initiator which builds a livingpolymer backbone at each lithium site. Typical monolithium livingpolymer structures containing conjugated diene hydrocarbon monomers are:

    ______________________________________                                        X--B--Li           X--B.sub.1 --B.sub.2 --Li                                    X--A--B--Li X--A--B.sub.1 --B.sub.2 --Li                                      X--A--B--A--Li                                                              ______________________________________                                    

wherein B represents polymerized units of one or more conjugated dienemonomers such as butadiene or isoprene, A represents polymerized unitsof one or more vinyl aromatic monomer such as styrene, and X is theresidue of a monolithium initiator such as sec-butyllithium. B can alsobe a copolymer of a conjugated diene and a vinyl aromatic compound. B₁and B₂ are formed of different dienes.

Dihydroxylated polydiene diols used in this invention may also beprepared anionically such as described in U.S. Pat. Nos. 5,391,663,5,393,843, 5,405,911, and 5,416,168 which are incorporated by referenceherein. The dihydroxylated polydiene polymer can be made using adi-lithium initiator, such as the compound formed by reaction of twomoles of sec-butyllithium with one mole of diisopropenylbenzene. Thisdiinitiator is used to polymerize a diene in a solvent typicallycomposed of 90% w cyclohexane and 10% w diethylether. The molar ratio ofdiinitiator to monomer determines the molecular weight of the polymer.The living polymer is then capped with two moles of ethylene oxide andterminated with two moles of methanol to yield the desired dihydroxypolydiene.

Dihydroxylated polydiene polymers can also be made using a mono-lithiuminitiator which contains a hydroxyl group which has been blocked as thesilyl ether. Details of the polymerization procedure can be found inU.S. Pat. No. 5,376,745 which is herein incorporated by reference. Asuitable initiator is hydroxypropyllithium in which the hydroxyl groupis blocked as the tert-butyl-dimethylsilyl ether. This mono-lithiuminitiator can be used to polymerize isoprene or butadiene in hydrocarbonor polar solvent. The living polymer is then capped with ethylene oxideand terminated with methanol. The silyl ether is then removed by acidcatalyzed cleavage in the presence of water yielding the desiredpolymer.

A dihydroxy polybutadiene unsaturated polymer within the scope of thisinvention can have any butadiene microstructure. However, it preferablyshould have more than about 10% 1,2-butadiene addition in order tominimize its viscosity. A dihydroxy polybutadiene polymer to be usedafter hydrogenation can also have any butadiene microstructure. However,it is preferred that it have no less than about 30% 1,2-butadieneaddition because, after hydrogenation, the polymer would be a waxy solidat room temperature if it contained less than about 30% 1,2-butadieneaddition and, when used in the process of this invention, it would givea paste at room temperature instead of a low viscosity solution.Therefore, compositions based on a hydrogenated polybutadiene diolhaving less than about 30% 1,2-butadiene addition would have to becoated onto a substrate while the composition was at a temperature highenough that the composition is a homogeneous, low viscosity liquid.Alternatively, the composition could be dispersed in water while it ishot and then be handled as a waterborne dispersion. Although ahydrogenated polybutadiene having a 1,2-butadiene addition greater thanabout 30% will give compositions within this invention which are liquidsat room temperature, it is preferred that the 1,2-butadiene contentshould be between about 40 and 60% to minimize viscosity of thehydrogenated polybutadiene diol.

When one of the conjugated dienes is 1,3-butadiene and is to behydrogenated, the anionic polymerization of the conjugated dienehydrocarbons is typically controlled with structure modifiers such asdiethylether or glyme (1,2-diethoxyethane) to obtain the desired amountof 1,4-addition. As described in U.S. Pat. No. Re 27,145 which isincorporated by reference herein, the level of 1,2-addition of abutadiene polymer or copolymer can greatly affect elastomeric propertiesafter hydrogenation.

Linear unsaturated or hydrogenated polyisoprene diol polymers can alsobe used in these compositions. A dihydroxy polyisoprene polymer withinthe scope of this invention can have any isoprene microstructure.However, it preferably should have greater than 80% 1,4-addition of theisoprene, preferably greater than 90% 1,4-addition of the isoprene, inorder to reduce the viscosity of the polymer. Polyisoprene diols of thistype can be prepared by anionic polymerization in the absence ofmicrostructure modifiers that increase 3,4-addition of the isoprene. Thediene microstructures are typically determined by C¹³ nuclear magneticresonance (NMR) in chloroform.

The preferred method of making the polymers of the present inventioninvolves the use of lithium initiators having the structure: ##STR1##wherein each R is methyl, ethyl, n-propyl, or n-butyl and A" is analkyl-substituted or non-substituted propyl bridging group, including--CH₂ --CH₂ --CH₂ -- (1,3-propyl), --CH₂ --CH(CH₃)--CH₂ --(2-methyl-1,3-propyl), and --CH₂ --C(CH₃)₂ --CH₂ --(2,2-dimethyl-1,3-propyl), or an alkyl-substituted or non-substitutedoctyl bridging group, including --CH₂ --CH₂ --CH₂ --CH₂ --CH₂ --CH₂--CH₂ --CH₂ -- (1,8-octyl), because these initiators will initiatepolymerization of anionic polymers at surprisingly higher polymerizationtemperatures with surprisingly lower amounts of dead initiator (higherefficiency) than similar initiators wherein A" is replaced byalkyl-substituted or non-substituted butyl, pentyl, or hexyl bridginggroups, such as --CH₂ --CH₂ --CH₂ --CH₂ -- (1,4-butyl), --CH₂ --CH₂--CH₂ --CH₂ --CH₂ -- (1,5-pentyl), or --CH₂ --CH₂ --CH₂ --CH₂ --CH₂--CH₂ -- (1,6hexyl).

Certain hydroxylated polydiene polymers useful in the present inventionhave the structural formula

    HO--A--OH or (HO--A).sub.n --X                             (I)

wherein A is a homopolymer of a conjugated diolefin monomer, a copolymerof two or more conjugated diolefin monomers, or a copolymer of one ormore conjugated diolefin monomers with a monoalkenyl aromatichydrocarbon monomer, where n>1 and where X is the residue of a couplingagent. During the preparation of these hydroxylated polydiene polymers,it is possible to make some mono-functional polymer having thestructural formula HO--A, either by incomplete capping of the livingpolymer or by incomplete coupling via the coupling agent. Although it ispreferred that the amount of this mono-functional polymer is minimal,satisfactory crosslinked compositions within this invention can beachieved even when the amount of mono-functional polymer is as high as70% w of the hydroxylated polymer in the composition.

Other hydroxylated polydiene polymers useful in the present inventionhave the structural formula

    HO--A--S.sub.z --B--OH or (HO--A--S.sub.z --B).sub.n --X

or

    HO--S.sub.z --A--B--S.sub.y --OH or (HO--S.sub.z --A--B).sub.n --X (II)

wherein A and B are polymer blocks which may be homopolymer blocks ofconjugated diolefin monomers, copolymer blocks of conjugated diolefinmonomers, or copolymer blocks of diolefin monomers and monoalkenylaromatic hydrocarbon monomers, where S is a vinyl aromatic polymerblock, where y and z are 0 or 1, where n is greater than or equal to 2,and where X is the residue of a coupling agent.

These polymers may contain up to 60% by weight of at least one vinylaromatic hydrocarbon, preferably styrene. The A blocks and the B blockscan have a number average molecular weight of from 100 to 500,000,preferably 500 to 50,000, and most preferably 1000 to 20,000. The Sblock which may have a number average molecular weight of from 500 to50,000. Either the A or the B block may be capped with a miniblock ofpolymer, 50 to 1000 number average molecular weight, of a differentcomposition, to compensate for any initiation, tapering due tounfavorable copolymerization rates, or capping difficulties.

The molecular weights of the polymers are conveniently measured by GelPermeation Chromatography (GPC), where the GPC system has beenappropriately calibrated. The polymers can be characterized from thedata in the chromatogram by calculating the number-average molecularweight (Mn), by calculating the weight-average molecular weight (Mw) orby measuring the "peak" molecular weight. The peak molecular weight isthe molecular weight of the main specie shown on the chromatogram. Foranionically polymerized linear polymers, the polymer is nearlymonodisperse (Mw/Mn ratio approaches unity), and usually it isadequately descriptive to report the peak molecular weight of the narrowmolecular weight distribution observed. Usually, the peak molecularweight value is between Mn and Mw. For polydisperse polymers the numberaverage molecular weight should be calculated from the chromatograph andused. The materials used in the columns of the GPC are styrene-divinylbenzene gels or silica gels. The solvent is tetrahydrofuran and thedetector is a refractive index detector.

The polymers of this invention may be hydrogenated as disclosed in U.S.Pat. No. Reissue 27,145 which is herein incorporated by reference. Thehydrogenation of these polymers and copolymers may be carried out by avariety of well established processes including hydrogenation in thepresence of such catalysts as Raney Nickel, noble metals such asplatinum and the like, soluble transition metal catalysts and titaniumcatalysts as in U.S. Pat. No. 5,039,755 which is also incorporatedherein by reference. The polymers may have different diene blocks andthese diene blocks may be selectively hydrogenated as described in U.S.Pat. No. 5,229,464 which is also incorporated herein by reference.

The crosslinking agents which are useful in the present invention areamino resins. For the purposes of this invention, an amino resin is aresin made by reaction of a material bearing NH groups with a carbonylcompound and an alcohol. The NH bearing material is commonly urea,melamine, benzoguanamine, glycoluril, cyclic ureas, thioureas,guanidines, urethanes, cyanamides, etc. The most common carbonylcomponent is formaldehyde and other carbonyl compounds include higheraldehydes and ketones. The most commonly used alcohols are methanol,ethanol, and butanol. Other alcohols include propanol, hexanol, etc.CYTEC (formerly American Cyanamid) sells a variety of these aminoresins, as do other manufacturers. CYTEC's literature describes threeclasses or "types" of amino resins that they offer for sale. ##STR2##where Y is the material that bore the NH groups, the carbonyl source wasformaldehyde and R is the alkyl group from the alcohol used foralkylation. Although this type of description depicts the amino resinsas monomeric material of only one pure type, the commercial resins existas mixtures of monomers, dimers, trimers, etc. and any given resin mayhave some character of the other types. Dimers, trimers, etc. alsocontain methylene or ether bridges. Generally, Type 1 amino resins arepreferred in the present invention.

The following Type 1 amino resins can be used to achieve the purpose ofthe present invention: CYMEL® 303--a melamine-formaldehyde resin where Ris CH₃, CYMEL® 1156--a melamine-formaldehyde resin where R is C₄ H₉,CYMEL® 1141--a carboxyl modified melamine-formaldehyde resin where R isa mixture of CH₃ and i-C₄ ₉, CYMEL® 1170--a glycoluril-formaldehyderesin where R is C₄ H₉, and BEETLE® 80--a urea-formaldehyde resin whereR is C₄ H₉. All of these products are made by CYTEC and are described inthe American Cyanamid publication 50 Years of Amino Coating Resins,edited and written by Albert J. Kirsch, published in 1986 along withother amino resins useful in the present invention.

The butylated amino resins generally have fairly good compatibility withthe hydroxy functional polydiene polymers while the methylated aminoresins generally are incompatible with the hydroxy functional dienepolymers. However, the amino resins do not necessarily have to becompletely compatible with the polymer and give phase stable mixtureswhen merely mixed together because the partial reaction disclosed inthis invention can overcome this incompatibility, giving resins whichwill not phase separate.

The reinforcing agent is a low molecular weight material having at leasttwo functional groups which will react with the amino resin crosslinkerwhen the composition is heated. The number average molecular weightpreferably is from 60 to 600, most preferably 60 to 120. Suitablefunctional groups include primary and secondary alcohols as well asdicarboxylic acids or anhydrides. The equivalent weight of thereinforcing agent will usually be between about 30 and about 150 gramsper functional group, preferably between about 50 and 100 grams perfunctional group. The functionality of the reinforcing agent should beat least two and can be as high as desired with the proviso thatincreasing the functionality increases the polarity which adverselyaffects the compatibility of the reinforcing agent with the polydienediol. However, if the reinforcing agent can be blended or cooked intothe composition, the functionality is acceptable.

Reinforcing agents suitable for use in the present invention includeunsubstituted aliphatic diols such as ethylene glycol, 1,3-propane diol,1,4-butane diol, 1,6hexane diol, and dimer diol, substituted aliphaticdiols such as 1,2-propane diol, 2-methyl-1,3-propane diol (MP-diol fromArco), neopentyl glycol, 2-ethyl-1,3-hexane diol (PEP diol),2,2,4-trimethyl-1,3-pentane diol (TMPD diol), and2-butyl-2-ethyl-1,3-propane diol (BEPD diol), cycloaliphatic diols suchas cyclohexane dimethanol and 4,4-isopropylidenedicyclohexanol (HBPA),and aromatic diols such as 4,4-isopropylidenediphenol (Bisphenol A)(BPA). Triols such as glycerol, trimethylol ethane, and trimethylolpropane may also be used. Analogous unsubstituted and substitutedcarboxylic acids may also be used. Preferred materials for use hereinare aliphatic diols having 5 to 40 carbon atoms, especiallyalkyl-substituted aliphatic diols such as PEP diol, TMPD diol, and BEPDdiol because they are substituted, branched diols and, as such, are notas incompatible with the polydiene polymers as unsubstituted, straightchain diols.

A proton-donating acid catalyst is often, but not always, required toachieve the purposes of the present invention, i.e., crosslink thepolymer and reinforcer using the amino resin crosslinkers describedabove. Sometimes, a catalyst is not necessary such as when CYMEL 1141 isthe crosslinking agent because its acid functionality alone issufficient to catalyze the partial reaction needed to obtaincompatibility as well as subsequent crosslinking reactions. When acatalyst is used, it is normal that the amount of the acid catalyst usedrange from about 0.05 to about 4% w of the polymer/reinforcer/aminoresin mixture to be certain there is sufficient acid but an excess canbe undesirable. Most preferably, an amount from about 0.1 to about 2% wof the polymer/reinforcer/amino resin is used. The presence of a strongproton-donating acid is normally required to catalyze the crosslinkingreaction of many amino resins which are useful in the present invention.However, some medium strength and even relatively weak acids may also beeffective depending upon the amino resins used. Generally, the mostactive catalysts are those with the lowest pKa values. The followinglist of acid catalysts which may be used in the present invention isarranged according to increasing pKa value: mineral acids, Cycat® 4040catalyst (p-toluene sulfonic acid), Cyca® 500 catalyst(dinonylnaphthalene disulfonic acid), Cycat® 600 catalyst (dodecylbenzene sulfonic acid), oxalic acid, maleic acid, hexamic acid,phosphoric acid, Cycat® 296-9 catalyst (dimethyl acid pyrophosphate),phthalic acid and acrylic acid. Other acids which may be used aredescribed in the aforementioned American Cyanamid Company publication.Also, 3M Brand Resin Catalyst FC-520 (diethylammonium salt oftrifluoromethane sulfonic acid) may be used. Cycat® 600 was found to bea very useful catalyst.

The compatible compositions of the present invention are prepared bymixing the polydiene polymer, the amino resin crosslinker, and thereinforcer together. An effort should be made to make the mixture ashomogeneous as is reasonably possible. The components are then partiallyreacted (incompletely reacted) in an appropriate vessel. It is importantthat the reaction not proceed too far or the composition will be toohigh in viscosity, making application very difficult or impossible orthe composition may even crosslink in the vessel. But, enough reactionmust be accomplished to overcome incompatibility of the components togive a resin which will not phase separate upon standing, or morepreferably, is homogeneous and clear. Conditions for cooking aparticular composition which will give a satisfactory product dependconsiderably on the composition and must be determined empirically foreach composition. For example, it was found that when cooking a resincontaining an acid-functional melamine resin, the acid on the resin wasusually sufficient to catalyze the reaction so little or no extracatalyst was needed. It was also found that cooking a resin containing arelatively incompatible methylated melamine at 100° C. for 1 hour wasnot sufficient to give a phase stable composition, cooking 2 hours wassatisfactory, and cooking 4 hours caused the resin to gel. Cookinganother composition containing the more compatible butylated melamineresin for 1 hour at 100° C. was satisfactory to give a clear, phasestable composition. Thus, satisfactory cooking conditions will be thosecombinations of catalyst concentration, cooking time, and cookingtemperature which are sufficient to give a phase-stable, preferablyclear composition. Thus, general recommendations are to do the reactionsat 60 to 120° C. for 0.5 to 10 hours, usually about 1 to 3 hours, in thepresence of a small portion of catalyst. The catalyst can be the sameone which will be needed to entirely crosslink the composition after ithas been applied to the substrate and is baked. It is frequently foundthat the amount of catalyst needed in the partial reaction step isusually less than about half of the total catalyst needed to obtain thedesired amount of crosslinking in the final product. The partiallyreacted mixture is then still in a physical form that allows convenientand easy application thereof as desired.

The partially reacted mixture and the rest of the catalyst required forcrosslinking are then mixed together and the mixture is applied to asubstrate. The substrate is then baked at 100 to 250° C. for 0.01 to 2hours to effect crosslinking.

Although use of solvent may not be necessary, solvent can be included inwith the polymer/reinforcer/amino resin mixture to reduce the viscositysuch that the partially reacted mixture can be easily stirred during thepartial reaction or to facilitate application of the finished resin.Suitable solvents include hydrocarbon solvents such as naphtha, mineralspirits, toluene, xylene, etc., and oxygenated solvents such as esters,ketones, ethers and alcohols. Two common solvents which are well suitedand which were used in much of this work are naphtha and isobutylacetate. If the partially reacted resin will be dispersed in water forapplication as a water based product, use of a water soluble solvent,such as BUTYL OXITOL or diacetone alcohol, may be advantageous. Solventcontents of up to 70% w of the polymer/reinforcer/amino resin/solventmixture can be used. However, it is usual with these compositions thatthe solvent content is 40% by weight or less.

For applications in which the resin must have low viscosity but in whichsolvent content must be low or even zero, it may be necessary todisperse the partially reacted resin in water and apply it as awaterborne composition. In this case, the partial reaction andsubsequent dispersion should be done with little or no solvent present.Dispersion of the partially reacted resin in water can be accomplishedeither by the inversion process or by the direct emulsification process.In the inversion process, the surfactant is added to the organic phasewhich has been heated to a temperature high enough to give the resin aviscosity low enough that it can be efficiently stirred. Typicaltemperatures are from about 40 to about 90° C. While stirring the resinvigorously, as with a 4-bladed stirrer rotating at about 2000 rpm, wateris slowly added. When a volume of water about equal to the volume of theorganic phase has been added, the mixture will invert from organiccontinuous to water continuous, thereby making the waterbornedispersion. More water is then added to reduce the viscosity to thedesired range. In the direct emulsification process, surfactant is addedto the required amount of water, typically about 150 parts by weight per100 parts of organic resin. The organic resin is then dispersed in thesoapy water with a high shear mixer, such as a Silversonmixer/emulsifier operating at about 6000 rpm. A wide variety ofsurfactants could be used, including anionic surfactants, nonionicsurfactants and cationic surfactants. A particularly effectivesurfactant is the anionic surfactant made by neutralizing CYCAT® 600with a tertiary amine such as triethyl amine or dimethylaminoethanol.This compound not only functions as the surfactant to stabilize thedispersion in water but, after the composition is applied to asubstrate, the amine evaporates during the bake step, allowing the CYCAT600 to catalyze the cure with the amino resin.

In the solids portion of the crosslinkable composition, the hydroxyfunctional diene polymer should comprise from 10 to 80 percent by weight(% w) of the polymer/reinforcer/crosslinker composition. The reinforcingagent should comprise from 2 to 40% w of the composition, and the aminoresin should comprise from 8 to 60% w of the composition. If the polymeris used at less than 10% w, then the cured composition will be toobrittle for most applications. If it is used at more than 80%, then theconcentrations of crosslinker and reinforcer will be too low and thecomposition will not cure to high strength and will be too soft for manyapplications. If the concentration of the reinforcer is too low, thenthe cured composition will be too soft for many applications, and if itis too high, then the crosslink density will be too high and thecomposition will again be too brittle. If the concentration of the aminoresin is too low, then the strength will not be as high as desired, andif the concentration is too high, then homopolymerization of the aminoresin will cause the cured composition to be too brittle.

The crosslinked materials of the present invention are most useful incoatings, especially in coatings applications which require hard, glossysurfaces such as coatings for metal buildings or furniture or coatingsfor difficult to bond to substrates such as oily metal or plasticsubstrates. They are also useful in certain kinds of adhesives(including assembly adhesives, structural adhesives, laminatingadhesives and contact adhesives), sealants, films (such as thoserequiring heat and solvent resistance), etc. However, it may benecessary for a formulator to combine a variety of ingredients togetherwith the compositions of the present invention in order to obtainproducts having the proper combination of properties (such as adhesion,cohesion, durability, low cost, etc.) for particular applications. Thus,a suitable formulation might be only the partially reacted resinconsisting of the polymers of the present invention, the reinforcingagent and the amino resin curing agent. However, in many adhesive,sealant and coating applications, suitable formulations would alsocontain various combinations of resins, plasticizers, fillers, solvents,stabilizers, surfactants and other ingredients such as asphalt. Thefollowing are some typical examples of formulating ingredients foradhesives, sealants and coatings.

In adhesive applications, as well as in coatings and sealants, it may benecessary to add an adhesion promoting or tackifying resin that iscompatible with the composition. A common tackifying resin is adiene-olefin copolymer of piperylene and 2-methyl-2-butene having asoftening point of about 95° C. This resin is available commerciallyunder the tradename Wingtack® 95 and is prepared by the cationicpolymerization of 60% piperylene, 10% isoprene, 5% cyclo-pentadiene, 15%2-methyl-2-butene and about 10% dimer, as taught in U.S. Pat. No.3,577,398. Other tackifying resins may be employed wherein the resinouscopolymer comprises 20-80 weight percent of piperylene and 80-20 weightpercent of 2-methyl-2-butene. The resins normally have ring and ballsoftening points as determined by ASTM method E28 between about 80° C.and 115° C. In some cases, however, liquid resins may also be used.

Other adhesion promoting resins which are also useful in thecompositions of this invention include hydrogenated rosins, esters ofrosins, polyterpenes, terpenephenol resins, polymerized mixed olefins,aromatic resins including coumarone-indene resins, polystyrene resins,vinyl toluene-alpha methylstyrene copolymers and polyindene resins. Toobtain good thermo-oxidative and color stability, it is preferred thatthe adhesion promoting resin be a saturated resin, e.g., a hydrogenateddicyclopentadiene resin such as Escorez® 5000 series resin made by Exxonor a hydrogenated polystyrene or polyalphamethylstyrene resin such asRegalrez® resin made by Hercules. The amount of adhesion promoting resinemployed varies from 0 to 200 parts by weight per hundred parts ofpartially reacted resin (phr), preferably between 20 to 150 phr, mostpreferably 20 to 100 phr. The selection of which particular adhesionpromoting resin to use is, in large part, dependent upon the specificcomposition of the partially reacted resin employed in the respectiveadhesive composition.

The composition of the instant invention may contain plasticizers, suchas rubber compounding oils. Rubber compounding oils are well-known inthe art and include both high saturates content oils and high aromaticscontent oils. Preferred plasticizers are highly saturated oils, e.g.Tufflo® 6056 and 6204 oil made by Arco and process oils, e.g. Shellflex®371 oil made by Shell. The amounts of rubber compounding oil employed inthe invention composition can vary from 0 to about 200 phr, preferablybetween about 0 to about 100 phr, and most preferably between about 0and about 50 phr.

This invention provides a process for painting a substrate requiringpriming, such as steel, which comprises: (a) coating the substrate witha primer selected from the group consisting of epoxy resin primers andpolyester resin primers, (b) applying to the primed substrate acrosslinkable basecoat composition comprising from 10 to 80 percent byweight of a dihydroxylated polydiene polymer, from 8 to 60 percent byweight of an amino resin crosslinking agent, and from 2 to 40 percent byweight of a reinforcing agent, and (c) applying over the basecoat aclearcoat selected from the group consisting of dihydroxypolydiene-based clearcoats, polyester clearcoats, and acrylicclearcoats.

The primers which may be used in the process of the present inventionare those which are commonly used as primers for steel substratesincluding epoxy resin primers and polyester primers. Epoxy resin primersare normally based on the diglycidyl ether of Bisphenol A (DGEBA), suchas EPON® 828 resin (Shell Chemical). To prepare the resin, the DGEBA isreacted with Bisphenol A (BPA) to generate a higher molecular weightepoxy resin which has secondary hydroxyl functional groups. The curingagent for this epoxy polyol is typically an amino resin or apolyisocyanate. After being suitably formulated, the epoxy primer can beapplied from solution in a solvent such as xylene or it can be appliedas a solvent free powder. A particularly desirable method of applyingthe epoxy primer is by the cathodic electrodeposition (CED) process. Atypical resin preparation and formulation of a waterborne epoxy primerwhich can be applied by the CED process is given in U.S. Pat. No.4,883,572 which is herein incorporated by reference. Again the DGEBA isreacted with BPA to give a higher molecular weight epoxy polyol. Theepoxy groups on the resin are then reacted with a secondary amine, suchas methylaminoethanol, and the tertiary amine formed is ionized with anacid, such as lactic acid. The ionic species make the resin dispersablein water. After formulating the resin with suitable curing agent,corrosion inhibitor package, and various other components, the primercan be applied and cured by baking, typically for 20 minutes at about180° C.

Polyester polyols can also be used in the primers. These polyesterpolyols are also normally cured with amino resins or polyisocyanates.Typically, the polyester polyols are synthesized by carrying out acondensation reaction using a glycol or a mixture of glycols and ananhydride or diacid compound or a mixture of anhydrides or diacidcompounds. The condensation reactions typically are done at temperaturesof 175 to 235° C. in a resin kettle which is capable of removing thewater of condensation. Typical glycols used in the polyester polyolsynthesis are the same as the reinforcing agents described above for usein the novel coating compositions of this invention. Especiallypreferred are ethylene glycol, 1,4-butane diol, and neopentyl glycol.The anhydrides and diacids which can be used in the polyester synthesisare well known. Anhydrides and diacids which are frequently used inpolyesters for primers are phthalic anhydride, isophthalic acid, andadipic acid. A fairly complete list of hydroxy functional and acidfunctional compounds which are used in polyesters is given in BulletinIP-65c, "How to Process Better Coating Resins with Amoco PIA and TMA"from Amoco Chemical Company, 1992.

Polyester primers can be applied from a solution in organic solvent oras a solvent free powder. However, a preferred method of application isas a waterborne coating. The technology for preparation of waterbornepolyester coating resins can be found in U.S. Pat. No. 4,054,614 whichis herein incorporated by reference. A polyester is prepared which hasacid functional groups. These acid groups are neutralized with atertiary amine, such as dimethylaminoethanol, and the resin is dispersedin water. After formulation with suitable crosslinkers, corrosioninhibitors, and any other ingredients necessary to give goodperformance, the primer is applied and cured by baking, typically for 30minutes at about 150° C.

Curing agents for the primers are typically amino resins orpolyisocyanates. The amino resins which are used are the same typeswhich are described above for use in the compositions of this invention.Polyisocyanates used in primers are usually based on toluenediisocyanate (TDI) or 4,4-diphenyl methane diisocyanate (MDI). Thesediisocyanates are typically converted to triisocyanates by, for example,condensing 3 moles of diisocyanate to form an isocyanurate ringstructure or by reaction of 3 moles of diisocyanate with a triol such astrimethylolpropane. The polyisocyanate will cure the polyol at ambienttemperature in a two component coating. Alternatively, the isocyanategroups can be blocked with a volatile blocking agent, such as phenol,and the blocked polyisocyanate will deblock when baked at temperaturesof about 180° C., regenerating the polyisocyanate which will cure thepolyol.

The primary functions of the primer coating are to prevent corrosion ofthe substrate, to provide a surface which is smooth or which can besanded smooth, and to provide a surface to which an additional coatingwill adhere. It has been found that the coatings of this inventionadhere very well to these primers. The coatings (basecoats) of thisinvention will almost always be pigmented to provide the desired colorto the coated part and also to protect the primer again degradation bysunlight and the environment. In other words, the basecoat is the"paint" for the substrate. This pigmented coating based on thecompositions of this invention will frequently also be coated with aclearcoat coating (clearcoat) to improve the appearance of the coatedpart and also to protect the pigmented coating against degradation.

Resins for the clearcoat coatings typically will contain either apolyester polyol or an acrylic polyol and the curing agent for thepolyol will be either an amino resin or a polyisocyanate. The polyesterpolyols in the clearcoat are very similar to those in the primer exceptthat only alcohol and acid functional components which have goodstability, especially to sunlight, will be used in the polyestersynthesis. The acrylic polyols used in clearcoats are made by freeradical polymerization, usually in solution in an organic solvent or ina suspension polymerization if the coating will be applied as a powder.There is a wide variety of acrylate and methacrylate monomers which arecommercially available for use in acrylics. The acrylic monomers whichwill be used in polymerization will be selected to give the acrylicpolyol the proper properties. Two of the important properties of theacrylic polyol are its glass transition temperature (which will usuallybe between 0 and 50° C.) and its hydroxy equivalent weight (which willusually be between 200 and 1000). Thus, a typical polymerization mightuse a combination of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate.

The crosslinkers for the polyester polyol or acrylic polyol in theclearcoat will be quite similar to those in the primers except that onlystable crosslinkers will be used. The amino resins of the type describedabove for use in the compositions of this invention are used ascrosslinkers for baked clearcoats. Only light stable isocyanates will beused. These are based on hexane diisocyanate (HDI), isophoronediisocyanate (IPDI) or 4,4-dicyclohexyl methane diisocyanate (HMDI).These diisocyanates will usually be converted to triisocyanates and theywill be blocked if they will be used to cure the polyol in a bakesystem. The clearcoat coatings will usually be formulated with wettingagents to improve flow and reduce surface defects, and with stabilizers,especially to protect the clearcoat as well as the basecoat againstdegradation by sunlight.

Optional components of the present invention are stabilizers.Antioxidants are added to protect the compositions against heatdegradation and oxidation during the preparation, storage, cure, and useof the compositions. Ultraviolet light stabilizers are added to protectthe compositions against degradation cause by sunlight.

Pigments will often be included in the coating (paint) composition togive the painted part the desired color and appearance. Various types offillers can be included in the formulation. This is especially true forexterior coatings or sealants in which fillers are added not only tocreate the desired appeal but also to improve the performance of thecoatings or sealants such as their weatherability. A wide variety offillers can be used. Suitable fillers include calcium carbonate, clays,talcs, silica, zinc oxide, titanium dioxide and the like. The amount offiller usually is in the range of 0 to about 65% w based on the solventfree portion of the formulation depending on the type of filler used andthe application for which the coating or sealant is intended. Anespecially preferred filler is titanium dioxide because it is veryeffective at improving resistance of compositions to degradation byexposure to sunlight.

The only three ingredients that will always be used in all adhesives,coatings or sealants of this invention are the hydroxy functional dienepolymer, the amino resin curing agent, and the reinforcing agent. Beyondthese ingredients, the formulator will choose to use or not to use amongthe various resins, fillers and pigments, plasticizers, stabilizers andsolvents disclosed herein. No definite rules can be offered about whichingredients will be used. The skilled formulator will choose particulartypes of ingredients and adjust their concentrations to give exactly thecombination of properties needed in the composition for any specificadhesive, coating or sealant application.

Adhesives are frequently thin layers of sticky compositions which areused in protected environments (adhering two substrates together).Therefore, unhydrogenated diene polymers will usually have adequatestability so resin type and concentration will be selected for maximumstickiness without great concern for stability, and pigments willusually not be used.

Coatings are frequently thin, non-sticky, pigmented compositions appliedon a substrate to protect or decorate it. Therefore, hydrogenated dienepolymers may be needed to give adequate durability. Resins will beselected to assure maximum durability and minimum dirt pick-up. Fillersand pigment will be selected carefully to give appropriate durabilityand color. Coatings will frequently contain relatively high solventconcentration or will be waterborne dispersions to allow easyapplication and give a smooth dry coating.

Sealants are gap fillers. Therefore, they are used in fairly thicklayers to fill the space between two substrates. Since the twosubstrates frequently move relative to each other, sealants are usuallylow modulus compositions capable of withstanding this movement. Sincesealants are frequently exposed to the weather, hydrogenated polymersare usually used. Resins and plasticizers will be selected to maintainlow modulus and minimize dirt pick-up. Fillers and pigment will beselected to give appropriate durability and color. Since sealants areapplied in fairly thick layers, solvent content is as low as possible tominimize shrinkage.

A formulator skilled in the art will see tremendous versatility in thehydroxy functional diene polymer/reinforcer/crosslinker compositions ofthis invention to prepare coatings, adhesives and sealants havingproperties suitable for many different applications.

EXAMPLES

The following examples demonstrate the utility of the inventivecompositions containing hydroxy terminated polydiene polymers, aminoresins, and reinforcing agents which have been cooked to obtaincompatibility and subsequently cured. The polymers used in the examplesare characterized in Table 1 where Bd is an unhydrogenated polybutadieneblock, EB is a hydrogenated polybutadiene block, and S/EB indicates arandom copolymer block of styrene and hydrogenated butadiene.

                  TABLE 1                                                         ______________________________________                                                                Func- 1,2-Bd  Styrene                                   Polymer Type M.sub.n tionality Content, % Content, % w                      ______________________________________                                        A     HO-EB-OH   3300   1.9   48      0                                         B HO-Bd-OH 3400 1.9 40 0                                                      C HO-EB-OH 2000 1.9 84 0                                                      D HO-EB-OH 2700 2.4 20 0                                                      E HO-S/EB-OH 3500 1.85 40 26                                                  F HO-S/EB-OH 4300 1.8 37 43                                                 ______________________________________                                    

Thus, Polymer A was a hydrogenated polybutadiene diol having a numberaverage molecular weight of 3300, an average functionality of 1.9hydroxyls per molecule, and a 1,2-Bd/1,4-Bd addition ratio of 48/52.Polymer B was a diol similar to Polymer A except the polybutadiene wasnot hydrogenated. Polymer C was similar to Polymer A except the1,2-Bd/1,4-Bd ratio was 84/16. Polymer D was similar to Polymer A exceptthe average functionality was 2.4 hydroxyls per molecule and the1,2-Bd/1,4-Bd ratio was 20/80. Polymers E and F were similar to PolymerA except they also contained 26% w and 43% w styrene copolymerized withthe hydrogenated polybutadiene.

The other components used in the examples are described in Table 2.

                  TABLE 2                                                         ______________________________________                                        Component    Supplier  Description                                            ______________________________________                                        Crosslinkers                                                                    CYMEL 1141 CYTEC Acid-functional,                                               methylated/butylated melamine/                                                formaldehyde, eq wt 150                                                                          -250                                                     CYMEL 1156 CYTEC Liquid, butylated                                              melamine/formaldehyde resin,                                                  2.2 functionality                                                           CYMEL 303 CYTEC Liquid, methylated                                              melamine/formaldehyde resin,                                                  2.2 functionality                                                           DESMODUR BL-3175 Bayer Blocked HDI based triisocyanate                        Catalyst                                                                      CYCAT 600 CYTEC Dodecylbenzene sulfonic acid                                  DABCO T-12 Air Products Dibutyl tin dilaurate                                 Reinforcing Diols                                                             TMPD Diol Eastman 2,2,4-trimethyl-1,3-pentane diol,                             mp = 54° C.                                                          BEPD Diol Eastman 2-butyl-2-ethyl-1,3-propane diol,                             mp = 40° C.                                                          HBPA Shell 4,4-                                                                 isopropylidenedicyclohexanol,                                                 mp = 160° C.                                                         BPA Shell 4,4-isopropylidenediphenol,                                           mp = 155° C.                                                         Solvents                                                                      VM&P Naphtha HT Shell Aliphatic hydrocarbon mixture,                            bp = 119-139° C.                                                     Isobutyl acetate Aldrich Isobutyl acetate, bp = 116° C.                Other Components                                                              DESMOPHEN 670A-80 Bayer Polyester polyol, 80% w in                              butyl acetate, 500 hydroxy eq wt                                            DESMOPHEN 365 Bayer Acrylic polyol, 65% w in butyl                              acetate/xylene (3/1),                                                         607 hydroxy eq wt                                                           TiPure R-706 DuPont Titanium dioxide pigment                                ______________________________________                                    

Coatings made according to the present invention were evaluated formechanical properties after they were applied to a substrate and curedby baking. The general appearance (clarity, gloss, adhesion, and marresistance) of the coatings was judged visually and describedqualitatively. The pencil hardness (gouge) of the coatings was measuredaccording to the ASTM D3363 method of pushing successively softer pencilleads across the coating until the pencil lead will no longer gougethrough the coating. The hardness scale (softest to hardest) is

    6B<5B<4B<3B<2B<B<HB<F<H<2H <3H<4H<5H<6H

Rocker hardness was measured by ASTM D2134 using a Sward type hardnessrocker. This test measures the number of rocks the rocker will make onthe coating before the amplitude decreases from a fixed starting angleto a fixed ending angle. The value is expressed as the percentage ofrocks the test sample gave relative to the number of rocks the rockerwould make on a glass substrate. The methyl ethyl ketone (MEK)resistance of the coatings was measured according to the ASTM D4752method of rubbing an MEK-moistened cloth across the coating for 100cycles, or until breakthrough to the metal substrate occurred (one cycleequals one forward and one backward stroke). It should be cautionedthat, in cases where the coatings had poor adhesion to steel, thehardness and MEK resistance values may be misleading since the coatingsmay be merely scraped off the steel instead of being gouged through orrubbed through. This poor adhesion to steel would have the effect ofmaking the coatings appear softer in the hardness test than they reallyare and making them appear poorly cured in the MEK resistance test whenthey actually may be well cured. Adhesion of the coatings was measuredwith the crosshatch adhesion test, ASTM D3359, Method B. In this test, alattice pattern is scribed through the coating, pressure sensitive tapeis applied and removed, and the amount of coating removed with the tapeis rated. The scale ranges from 5 (no adhesion loss) to 0 (greater than65% adhesion loss).

An integral part of this invention is the process of cooking thecomponents of these compositions to overcome their inherentincompatibility. Conditions of catalyst concentration, cooking time, andcooking temperature necessary to prepare phase stable compositionsvaried from one formulation to another and had to be determined by trialand error for each formulation. Phase stable combinations of thepolymer, reinforcer, and crosslinker could usually be obtained bycooking them together in a resin kettle for about 1-3 hours at about100° C. using varying amounts of acid catalyst, CYCAT 600. The catalystconcentration, cooking time, and cooking temperature actually used foreach composition is shown in the tables. For convenience, the cooks weretypically done at 60% w solids content in solvent, either isobutylacetate or VM&P naphtha, to give the resin a manageable viscosity.Viscosities at 25° C. were measured on some of the compositions using aBrookfield viscometer. Prior to casting films, the acid catalyst contentwas typically increased to 1 part by weight (pbw) in order to accomplishcure during bake. Unless specified otherwise, coatings were applied oncold rolled steel panels (QD412 panels from Q-Panel Corp.) with a #52wire wound rod and cured by baking 20 minutes at 175° C. Coatings wereapplied on thermoplastic olefin panels (Himont ETA-3081 panels from ACTCorp.) and cured by baking 1 hour at 121° C.

Comparative Example

Table 3 presents properties of coatings made with Polymer A using theconventional technology of curing diols with melamine resins, withoutthe reinforcing agents of this invention.

                  TABLE 3                                                         ______________________________________                                        Composition, pbw                                                                             3-1         3-2     3-3                                        ______________________________________                                        Polymer A      80          80      80                                           CYMEL 303 20 -- --                                                            CYMEL 1156 -- 20 --                                                           CYMEL 114 -- -- 20                                                            CYCAT 600   0.4   0.4  0                                                      VM&P naphtha 67 67 --                                                         Isobutyl acetate -- -- 67                                                     Cook Time,hr  1  1  1                                                         Cook Temp,° C. 100  80 100                                             Appearance of Resin                                                           Phase stable? yes yes no                                                      Clarity clear clear grainy                                                    Viscosity @ 25° C., cps 15000   nd --                                  Properties on QD412                                                           Thickness, mil   1.0   0.6 --                                                 Pencil Hardness B 4 B --                                                      MEK Rubs  4  2 --                                                             Crosshatch Adhesion  0  0 --                                                  General Appearance                                                            Clarity clear clear --                                                        Gloss high high --                                                            Adhesion to Steel v. Poor v. Poor --                                          Mar Resistance v. poor v. Poor --                                             Properties on ETA-3081                                                        Crosshatch Adhesion  5  5 --                                                ______________________________________                                    

The results show that conditions of 0.4 pbw of catalyst and cooking 1hour at 100° C. were sufficient to give a phase stable composition withFormulation 3-1. The butylated melamine, CYMEL 1156, used in Formulation3-2 is somewhat more compatible with Polymer A and so the somewhat moremild cooking temperature of 80° C. was sufficient to give a phase stablecomposition. No combination of cooking time, temperature, and catalystconcentration was found which gave a satisfactory composition withFormulation 3.3. The acid functionality on the CYMEL 1141 seemed tocatalyze the reaction so no CYCAT 600 was needed. In fact, when aslittle as 0.4 pbw of CYCAT 600 was added, the resin gelled quicklyduring the resin cook. When cook times shorter than 1 hour were used,the resins made were not phase stable and would separate upon standingat room temperature. When cook times longer than 1 hour were used, theresin became too high in viscosity and, after several hours of cooking,the resin gelled.

The results in Table 3 show that both Formulations 3-1 and 3-2 had pooradhesion to unprimed steel but excellent adhesion to thermoplasticpolyolefin (TPO) substrate. However, both compositions gave coatingswhich were very soft and weak, thus giving them very poor mar resistanceand making them unsuitable for use in practical applications.

The results of the Comparative Example show that, to be useful, coatingsbased on the hydroxy terminated polydiene polymers and melamine resinswill have to be harder and stronger. This could be accomplished by alsoincluding a low molecular weight reinforcing diol, such as TMPD diol orBEPD diol, in the formulation. But these low molecular weight diols arequite polar and therefore have poor compatibility with the hydroxyterminated polydiene polymers described above and mixtures with them arenot phase stable. However, this invention demonstrates that phase stablecompositions can be prepared containing the reinforcing diols bycarrying out the partial reaction of the components using the method ofthis invention as described above. The results of experiments whichdemonstrate this invention are given in Tables 4, 5, 6 and 7.

Example 1 Effect of Melamine Resin and Reinforcing Diol Type

Table 4 presents results on formulations containing two low molecularweight, branched, reinforcing diols with two butylated melamine resinsin formulations containing 40 pbw of Polymer A.

                  TABLE 4                                                         ______________________________________                                        Composition, pbw                                                                            4-1     4-2      4-3    4-4                                     ______________________________________                                        Polymer A     40      40       40     40                                        TMPD diol 20  20                                                              BEPD diol  20  20                                                             CYMEL 1156 40 40                                                              CYMEL 1141   40 40                                                            CYCAT 600   0.4   0.4  0  0                                                   VM&P naphtha 67 67 67 67                                                      Cook Time, hr  2  2  2  2                                                     Cook Temp., ° C. 100  100  100  100                                    Appearance of Resin                                                           Phase stable? yes yes yes yes                                                 Clarity clear clear clear clear                                               Viscosity @ 25° C., cps 125  230  170  205                             Properties on QD412                                                           Thickness, mil   1.3   1.0   1.0   0.9                                        Pencil Hardness HB 3 B H H                                                    MEK Rubs >100    22 100  >100                                                 Crosshatch Adhesion  0  0  1  0                                               General Appearance                                                            Clarity clear clear clear clear                                               Gloss high high high high                                                     Adhesion to Steel poor poor good poor                                         Mar Resistance good good good good                                            Properties on ETA-3081                                                        Crosshatch Adhesion  5  5  5  5                                             ______________________________________                                    

The results show that both TMPD diol and BEPD diol can be cooked intoresins based on Polymer A using either CYMEL 1156 or CYMEL 1141 to givephase stable compositions. Clear resins could be made with CYMEL 1156using 0.4 pbw of CYCAT 600 catalyst. Since the acid group on CYMEL 1141can catalyze the reactions, no CYCAT 600 was needed in the cooks withCYMEL 1141 to achieve phase stable blends. All four of the compositionshave much better mar resistance than the Comparative Example.Formulations 4-1 and 4-2 in Table 4 have very poor adhesion to steel andcan be rubbed off the steel readily with mild finger pressure.Formulations 4-3 and 4-4, containing the acid functional melamine resin,have much better adhesion in this qualitative test but still have lowadhesion to steel in the crosshatch adhesion test. All fourformulations, however, have excellent adhesion to TPO which is generallyconsidered to be a difficult substrate to adhere to.

Example 2 Effect of Concentration of Polymer A

The results in Table 5 show the effect of the concentration of thehydroxy terminated diene polymer in formulations containing TMPD diolwith two butylated melamine resins.

                  TABLE 5                                                         ______________________________________                                        Composition,                                                                    pbw 5-1 5-2 5-3 54 5-5 5-6                                                  ______________________________________                                        Polymer A                                                                              40      40      30    30    20    20                                   TMPD diol 20 20 20 20 30 30                                                   CYMEL 1156 40 -- 50 -- 50 --                                                  CYMEL 1141 -- 40 -- 50 -- 50                                                  CYCAT 600   0.4  0   0.4  0   0.4  0                                          VM&P naphtha 67 67 67 67 67 67                                                Cook Time, hr  2  2  2  2  2  2                                               Cook 100  100  100  100  100  100                                             Temp., ° C.                                                            Appearance                                                                    of Resin                                                                      Phase stable? yes yes yes yes yes yes                                         Clarity clear clear clear clear clear clear                                   Viscosity @ 125  170  75 150  40 60                                           25° C., cps                                                            Properties                                                                    on QD412                                                                      Thickness, mil   1.3   1.0   1.1   1.2   1.2   0.9                            Pencil HB H B H H H                                                           Hardness                                                                      MEK Rubs >100    100  >100    >100    >100    >100                            Crosshatch  0  1  0  0  0  0                                                  Adhesion                                                                      General                                                                       Appearance                                                                    Clarity clear clear clear clear clear s1. haze                                Gloss high high high high high good                                           Adhesion poor good poor good poor fair                                        to Steel                                                                      Mar Resistance good good excel excel excel excel                              Properties                                                                    on ETA-3081                                                                   Crosshatch  5  5  5  4  5 nd                                                  Adhesion                                                                    ______________________________________                                    

The results in Table 5 show that excellent resins can be obtained atconcentrations of Polymer A of only 20 pbw. Again it was found that 0.4pbw of CYCAT 600 was needed in the formulations containing CYMEL 1156 toachieve phase stable resins but no CYCAT 600 was needed in theformulations containing CYMEL 1141. All three of the coatings containingCYMEL 1156 had poor adhesion to steel while those containing CYMEL 1141adhere somewhat better to steel. Formulations 5-1 through 5-5 hadexcellent adhesion to TPO. Adhesion to TPO was not determined (nd) onFormulation 5-6 but it too is expected to show excellent adhesion toTPO.

Example 3 Effect of Type of Hydroxy Terminated Polydiene Polymer

The results in Table 6 show the effect of the type of hydroxy terminateddiene polymer used in the composition containing TMPD diol and CYMEL1141.

                  TABLE 6                                                         ______________________________________                                        Composition, pbw                                                                            6-1     6-2      6-3    6-4                                     ______________________________________                                        Polymer A     40      --       --     --                                        Polymer B -- 40 -- --                                                         Polymer C -- -- 40 --                                                         Polymer D -- -- -- 40                                                         TMPD diol 20 20 20 20                                                         CYMEL 114T 40 40 40 40                                                        VM&P naphtha 67 67 67 67                                                      Cook Time, hr  2  2  2  2                                                     Cook Temp., ° C. 100  100  100  100                                    Appearance of Resin                                                           Phase stable? yes yes yes yes                                                 Clarity clear clear clear opaque                                              Viscosity @ 25° C., cps 170  95 45 paste                               Properties on QD412                                                           Thickness, mil   1.0   1.1   1.1 --                                           Pencil Hardness H 4 H H --                                                    MEK Rubs 100  >100    >100    --                                              Crosshatch Adhesion  1  5  4 --                                               General Appearance                                                            Clarity clear clear clear --                                                  Gloss high high high --                                                       Adhesion to Steel good excel excel --                                         Mar Resistance good excel excel --                                            Properties on ETA-3081                                                        Crosshatch Adhesion  5  3  3 --                                             ______________________________________                                    

All four formulations were cooked for 2 hours at 100° C. withoutaddition of CYCAT 600 catalyst because CYMEL 1141 was used in allformulations. As is the case with nearly all the resins prepared in thiswork, all four resins were clear when hot after cooking was complete.Formulations 6-1, 6-2 and 6-3 remained clear when cooled to roomtemperature. However, Formulation 6-4 became an opaque, easily stirredpaste when cooled to room temperature. Thus, in practical applicationsFormulation 6-4 would have to be coated onto a substrate while it wasstill hot. Since equipment to do this was not available, Formulation 6-4was not coated and tested. However, its properties would be expected tobe similar to those of Formulation 6-1 based on Polymer A. Results onFormulations 6-1, 6-2, and 6-3 show that, although the compositions withPolymers B and C did not adhere to TPO as well as the composition withPolymer A, all three of Polymers A, B, and C are suitable for use inthis invention. Although more sophisticated equipment may be needed tocoat resins based on Polymer D, it is expected that Polymer D would alsobe suitable for use in this invention.

Example 4 Effect of Styrene Content in the Hydroxy Terminated DienePolymer

The results in Table 7 compare compositions made with hydroxy terminatedpolydiene polymers with varying styrene content with TMPD diol and themethylated melamine resin, CYMEL 303.

                  TABLE 7                                                         ______________________________________                                        Composition, pbw                                                                             7-1        7-2     7-3                                         ______________________________________                                        Polymer A      40         --      --                                            Polymer E -- 40 --                                                            Polymer F -- -- 40                                                            TMPD diol 20 20 20                                                            CYMEL 303 40 40 40                                                            CYCAT 600  1  1  1                                                            VM&P naphtha 67 67 67                                                         Cook Time, hr  3  3  3                                                        Cook Temp., ° C. 100  100  100                                         Appearance of Resin                                                           Phase stable? no yes yes                                                      Clarity v. Hazy clear clear                                                   Viscosity @ 25° C., cps nd 540  1300                                   Properties on QD412                                                           Thickness, mil --   1.2   1.1                                                 Pencil Hardness -- 4 B 3 B                                                    MEK Rubs -- >100    15                                                        Crosshatch Adhesion --  0  0                                                  General Appearance                                                            Clarity -- clear clear                                                        Gloss -- high high                                                            Adhesion to Steel -- poor poor                                                Mar Resistance -- excel excel                                                 Properties on ETA-3081                                                        Crosshatch Adhesion --  5  2                                                ______________________________________                                    

The results for Formulation 7-1 show that it was difficult to preparethis resin. Even under these fairly severe cooking conditions, the resinwas hazy and phase separated upon standing at room temperature. It isfelt that a phase stable composition could be made with Formulation 7-1with further work to optimize catalyst concentration and cookingconditions. The reason for this difficulty in preparing Formulation 7-1is the limited compatibility of Polymer A with CYMEL 303. Results onFormulations 7-2 and 7-3 show that Polymers E and F gave much betterresins in this formulation than did Polymer A. This shows the beneficialeffect of including styrene in the diol in improving compatibility withthe melamine resin. In this formulation, neither resin gave goodadhesion to steel but both adhered fairly well to the TPO.

Example 5 Adhesion of Various Coating Compositions to Primed Steel

A selection of coating compositions based on dihydroxy functionalpolydiene polymers was tested on steel panels which were primed with thecathodic electrodeposition (CED) epoxy primer specified for use on Fordcars. The resins were also tested on unprimed steel. The compositions ofthe resins are given in Table 8. All of the resins were prepared bycooking them in a resin kettle for 2 hours at 100° C. at 60% w solids inShell VM&P Naphtha solvent. All the resins were clear, nearly colorless,fairly low viscosity liquids. They were applied to the substrates with a#52 wire rod and were cured by baking 30 minutes at 121° C. Propertiesare shown in the Table 8.

                                      TABLE 8                                     __________________________________________________________________________    Adhesion of Various Basecoats to Steel.sup.a                                  Composition, pbw.sup.d                                                                      8-1 8-2 8-3 8-4 8-5 8-6                                         __________________________________________________________________________    Polymer A     40  30  30  30                                                    Polymer F (43% S)     40                                                      Polymer E (26% S)      40                                                     TMPD Diol 20 20   20 20                                                       HBPA.sup.e   20                                                               BPA    20                                                                     CYMEL 1156 40 50 50 50                                                        CYMEL 1141     40 40                                                          CYCAT 600  1  1  1  1  1  1                                                   VM&P Naphtha 67 67 67 67 67 67                                                Cook Time, hr  2  2  2  2  2  2                                               Cook Temp, C. 100  100  100  100  100  100                                    Properties on Unprimed Steel.sup.b                                            Thickness, mil   1.3   0.9     1.1   1.2                                      Pencil Hardness HB H   4 H 4 H                                                Rocker Hardness  12                                                           Crosshatch Adhesion  0  0    5  5                                             Properties on CED Primed Steel.sup.c                                          Thickness, mil   2.0   2.1   1.9   1.9   2.0   2.1                            Pencil Hardness H H H H 4 H 3 H                                               Rocker Hardness  5 11 15 10  6  6                                             Crosshatch Adhesion  5  5  5  5  5  5                                       __________________________________________________________________________     .sup.a Resins were cooked for 2 hours at 100° C. with 0.4 pbw CYCA     600 in a resin kettle. CYCAT level was raised to 1 pbw prior to casting       films. Coatings were applied onto the substrates with #52 wire rod. They      were cured by baking 30 minutes at 121° C.                             .sup.b Unprimed steel substrate was QD412 panels from QPanel Corp.            .sup.c CED primed steel was APR 16900 (Ford spec) from ACT.                   .sup.d pbw = parts by weight                                                  .sup.e Hydrogenated Bisphenol A                                          

The results of the crosshatch adhesion test show that the coatingcompositions based on the two styrene-containing diols, Polymers E and Fgive good crosshatch adhesion to unprimed steel since the acidfunctional melamine resin, CYMEL 1141, was used in these formulations.The results in Table 8 also show that all of the coating compositionsgave excellent crosshatch adhesion to the CED epoxy primed steel. Thus,any of these coating compositions would be a candidate for use incoatings over this epoxy primer. It is likely that the epoxy primercoating has residual functional groups which can react with the melamineresin in the coating composition giving excellent bonding between theprimer and the coating composition.

Example 6 Basecoat/Clearcoat Combinations

A system for painting a car would consist of at least three layers(primer/basecoat/clearcoat) or four layers(primer/surfacer/basecoat/clearcoat). Table 9 presents prototypeformulations for a basecoat and three clearcoats intended to demonstratethe suitability of resins based on Polymer A for use in automotivecoatings.

                  TABLE 9                                                         ______________________________________                                        Basecoat/Clearcoat Combinations                                                                White    Cooked Polyester                                                                            Acrylic                                 Coating Basecoat Clearcoat Clearcoat Clearcoat                                Composition, pbw 9-1 9-2 9-3 9-4                                            ______________________________________                                        Polymer A    40       30                                                        DESMOPHEN 670A-80   87.5                                                      DESMOPHEN 365    607                                                          TMPD Diol 20                                                                  BEPD Diol  20                                                                 CYMEL 1156 40 50                                                              CYMEL 303   30                                                                DESMODUR BL-3175    370                                                       CYCAT 600 1 1 1                                                               DABCO T-12    0.73                                                            IRGANOX 1076 0.5 0.5 0.5 3.6                                                  TINUVIN 328 1 2 2 14.6                                                        TINUVIN 123 2 2 1 7.3                                                         VM&P Naphtha HT 67 67                                                         Xylene   28 253                                                               TiPure R-706 100                                                            ______________________________________                                    

The resins in Basecoat 9-1 and Clearcoat 9-2 were cooked for 2 hours at100° C. with 0.4 pbw of CYCAT 600. Before casting films, the catalystlevel was increased to 1 pbw and the stabilizers (IRGANOX 1076, TINUVIN328, and TINUVIN 123, supplied by Ciba Geigy) were added. Basecoat 9-1used TiO₂ at 50% w on a solids basis as the pigment. Clearcoat 9-3 was apolyester polyol cured with a melamine resin and Clearcoat 9-4 was anacrylic polyol cured with a blocked isocyanate. All coatings werethinned as required to achieve a sprayable viscosity usingxylene/butanol (1/1).

The white Basecoat 9-1 was applied to three substrates; DEXFLEX 880(purchased from Standard Plaque, Inc.) is a TPO which is typical of thetype used in automobile bumpers, epoxy primed steel (APR 16900 purchasedfrom Advanced Coating Technologies, Inc.) which is the CED epoxy primerspecified for use by Ford, and primer/surfacer coated steel (APR 29401purchased from Advanced Coating Technologies, Inc.) which is specifiedfor use by Ford. After about a 5 minute flash, Clearcoat 9-2 was appliedover the coated epoxy primed steel, and the coatings were cured bybaking 30 minutes at 121° C. The white Basecoat 9-1 on TPO was cured bybaking 30 minutes at 121° C. and Clearcoat 9-3 was applied and cured bybaking 30 minutes at 121° C. The white Basecoat 9-1 on theprimer/surfacer coated steel was cured by baking 30 minutes at 121° C.Clearcoat 94 was applied over the coated primer/surfacer panels and theclearcoat was cured by baking for 20 minutes at 150° C. It was foundthat all three basecoat/clearcoat systems gave excellent adhesion in thecrosshatch adhesion test.

These results demonstrate that basecoat compositions based on thedihydroxy polydiene polymers are suitable candidates for use in coatingsnot only for TPO but also for the primed metal parts of the car as well.They have excellent crosshatch adhesion to TPO and to the primed metalsubstrates which are typically used by Ford. They also have excellentintercoat adhesion with polyester/melamine and acrylic/urethaneclearcoats as well as to clearcoats made from another dihydroxypolydiene resin.

I claim:
 1. A process for making a compatible crosslinked compositionwhich comprises the steps of:(a) mixing together from 10 to 80 percentby weight of a hydroxy functional polydiene polymer having afunctionality of at least 1.3, from 8 to 60 percent by weight of anamino resin crosslinking agent, and from 2 to 40 percent by weight of areinforcing agent which has at least two functional groups which willreact with the amino resin crosslinking agent, said functional groupsselected from the group consisting of hydroxyl, carboxylic acid oranhydride, or amide functionality, wherein the reinforcing agent has anequivalent weight from 30 to 150 grams per functional group, and (b)partially reacting the polydiene polymer, amino resin, and reinforcingagent at 60 to 120° C. for 0.5 to 10 hours, optionally in the presenceof a small amount of crosslinking catalyst, such that a phase-stablemixture is obtained, (c) applying the partially reacted mixture to asubstrate, and (d) crosslinking the applied mixture by baking at 100 to250° C. for 0.01 to 2 hours, optionally in the presence of additionalcrosslinking catalyst.
 2. The process of claim 1 wherein a crosslinkingcatalyst is used in a total amount of from 0.05 to 4% by weight and lessthan one half is used in step (b).
 3. The process of claim 2 wherein thetotal amount of catalyst used is from 0.1 to 2% by weight.
 4. Theproduct of the process of claim 1.